WO2009155291A1

WO2009155291A1 - Curable compositions containing urethane linkages for reworkable adhesives

Info

Publication number: WO2009155291A1
Application number: PCT/US2009/047528
Authority: WO
Inventors: Paul Morganelli; Xinnan Zhang; Osama M. Musa; Donald Herr; Shengqian Kong; Sharon Ann Chaplinsky
Original assignee: Henkel Corporation
Priority date: 2008-06-19
Filing date: 2009-06-16
Publication date: 2009-12-23
Also published as: TW201000580A

Abstract

A reworkable resin having an urethane linkage with a thermally curable terminal functionality is disclosed. The cured product of the reworkable resin is particularly useful to adhere electronic components to substrates where reworkability is desirable

Description

CURABLE COMPOSITIONS CONTAINING URETHANE LINKAGES

FOR REWORKABLE ADHESIVES

FIELD OF THE INVENTION

[0001] This invention relates to a thermally reworkable resin having at least one aromatic or aliphatic urethane linkage and at least one reactive terminal functionality. The urethane linkage of the reworkable resin degrades upon exposure to elevated temperature.

BACKGROUND OF THE INVENTION

[0002] Thermosetting resins have been widely used in variety of applications, such as coating, encapsulants, and adhesives. However, many traditional thermosetting resins display poor tractability after curing, which limits their use in those applications for which degradable or reworkable polymers are advantageous. For example, the reworkability of an adhesive used to adhere semiconductor chips to substrates is desired because it is expensive to discard a multi-chip package with only one failed chip. The use of an adhesive that will soften or decompose to allow chip repair or replacement would be an advantage for semiconductor manufacturers. Other industries would benefit similarly from the ability to use reworkable materials. Thus, there is a need for adhesives, coatings, and encapsulants that can be decomposed and reworked in many applications.

[0003] Current technologies include the use of thermoplastic or low glass transition (Tg) thermosetting materials to achieve reworkability. However, both thermoplastic and low Tg thermosetting materials lead to poor reliability.

[0004] U.S. Pat. Nos., 6,570,029 and 6,498,260 issued to Wong et al., disclose a reworkable underfill based on aliphatic epoxy and anhydride system. However, the use of anhydride-based material, when humidified, tends to cause delamination at the interface with chips in solder reflow. Furthermore, the use of anhydride has been linked to possible health and environmental hazards.

[0005] There continues to be a need in the art for a curable thermosetting resin that provides reworkability. The current invention addresses this need.

SUMMARY OF THE INVENTION

[0006] This invention relates to a thermally reworkable resin having at least one aromatic or aliphatic urethane linkage and at least one reactive terminal functionality. The at least one reactive terminal functionality is selected from methacrylate, acrylate, styrenic, vinyl ether and epoxy. The urethane linkage of the reworkable resin degrades upon exposure to elevated temperature.

[0007] The aromatic embodiment is directed to a resin having (1) at least one aromatic urethane group, wherein the aromatic group is directly connect to the N atom, O atom or both the N and the O atoms of the urethane. [0008] Another embodiment is directed to a cured composition prepared from the reaction of the resin

H ° and a curing agent. The resin has the structure: ^R1 N O R2 wherein R1 or R2, or both are, an aliphatic or aromatic group, with or without heteroatom; wherein R1 or R2, or both, have at least one reactive terminal group; and wherein there may be a spacer group between the aromatic group and the reactive terminal group. The reactive terminal group is selected from the group consisting of methacrylate, acrylate, styrenic, vinyl ether and epoxy. The spacer group may be aliphatic, cycloaliphatic, or aromatic, with or without heteroatom.

[0009] Another embodiment of the invention is directed to a reworkable composition wherein the resin having at least one aromatic or aliphatic urethane linkage and at least one reactive terminal functionality is cured with a peroxide, a super acid and/or an imidazole. In a further embodiment, the curing agent is free of urethane linkage.

[0010] In a further embodiment, the reworkable composition further comprises reactive diluents, adhesion promoters and/or inorganic fillers.

[0011] Yet in another embodiment, the cured composition is capable of softening under exposure to elevated temperature. Upon exposure to temperatures from about 18O⁰C to about 275°C, the urethane linkage in the composition decomposes and provides reworkablility.

[0012] In a further embodiment, the composition is applied to a first substrate and bonded and cured to at least a second substrate with the thermally reworkable composition, wherein at least one of the substrate is an electronic component and/or a semiconductor chip. The thermally reworkable composition is a cured product of a resin having a urethane linkage and at least one reactive terminal functionality with a curing agent.

[0013] Still another embodiment is directed to a method of adhering and reworking an electronic device, and/or electronic components, (herein "substrate" or "substrates") using the reworkable composition. The method of adhering comprises applying the composition onto a first substrate, for example, an electronic component, contacting a second substrate onto the composition, and curing the composition. The composition may be first applied to any of the substrates used in the manufacture of the device under fabrication, and multiple substrates (including devices and components) are contemplated. The method of reworking comprises heating the substrates containing the reworkable composition and removing the first substrate, cleaning the first substrate of the softened composition, applying new composition on the first substrate, contacting a second substrate onto the composition, and curing the composition.

[0014] Another embodiment provides an electronic device manufactured using the reworkable composition of the invention. Encompassed are flip chip on board, chip-scale packages, ball-grid arrays, and package-on-package components. BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0015] Figures I to V are NMR spectra of the reworkable compositions (I. isocyanatoethyl methacrylate/ bis-phenol A adduct; II. poly(propylene glycol)toluene diisocyanate/ glycidol adduct; III. iseugenol/ isocyanatoethyl methacrylate adduct; IV. polyMDI (methylene diphenyl diisocyanate)/ glycidol adduct; and V. methylene diphenyl diisocyanate/ glycidol adduct). Figures Vl and VII are hot-stage and isotherm hot-stage IR spectra of isocyanatoethyl methacrylate/ bis-phenol A adduct. Figure VIII is a thermal gravimetric analysis spectrum of isocyanatoethyl methacrylate/ bis-phenol A adduct. Figure IX is the ¹HNMR spectrum of TMXDI-Glycidol Adduct. Figure X is the ¹HNMR spectrum of IPDI-Glycidol Adduct.

DETAILED DESCRIPTION OF THE INVENTION [0016] The term "resin" herein is defined as any monomer, polymer or oligomer.

[0017] The term "reworkable resin" herein is defined as resin that can be removed with heat and/or solvent to allow for repair or replacement, especially in semiconductor packages.

[0018] The reworkable resin has (1) a urethane group, and (2) at least one reactive terminal group, such as methacrylate, acrylate, styrenic, vinyl ether and/or epoxy functionalities. In one embodiment the urethane group is an aromatic urethane group in which the aromatic group is directly connected to the N atom, the O atom, or both the N and the O atoms of the urethane

[0019] The reworkable resin having at least one urethane linkage and at least one reactive terminal group may be synthesized by various methods, including reaction of a mono- or multifunctional phenol or glycol with an isocyanate containing acrylate, methacrylate, or styrenic functionality; reaction of a mono-or multifunctional isocyanate with a phenol or alcohol containing acrylate, methacrylate, styrenic, vinyl ether, or epoxy functionality. The reaction may further include an organic solvent, such as toluene, and/or a catalyst, such as dibutyltin dilaurate or triethyl amine, and heated at 50-150 ⁰C for 0.5-13 hours.

[0020] In one embodiment, the reworkable resin may be formed by reacting a multifunctional phenol or glycol with two equivalents of an isocyanate compound containing acrylate, methacrylate, or styrenic functionality. The reaction of isocyanate compound containing acrylate, methacrylate or sytrenic functionality with a multifunctional phenol proceeds according to the following reaction scheme:

[0021] The isocyanate compound containing acrylate, methacrylate or sytrenic functionality will have the structure as shown in the above reaction scheme, in which A and B are independently selected from the group consisting of hydrogen, aliphatic, cycloaliphatic and aromatic groups with or without heteroatom; Y is independently selected from the group consisting of aliphatic, cycloaliphatic, and aromatic structures with or without heteroatom; J is independently selected from the group consisting of -N(R1)(R2), -SR3, - 0R3, Ar, or an alkyl group having 1-12 carbon atoms (Ar is an aromatic or heteroaromatic ring or fused ring having 3-10 carbon atoms within the ring structure, in which the heteroatom may be N, O, or S; R1 and R2 are independently selected from hydrogen, an alkyl group having 1-12 carbon atoms, or Ar as described above; R3 is an alkyl group having 1-12 carbon atoms, or is Ar as described above).

[0022] The multifunctional phenol will have the structure as shown in the above reaction scheme, in which X is independently selected from the group consisting of aliphatic, cycloaliphatic, and aromatic groups with or without heteroatom; G and Q are independently selected from the group consisting of - N(R1)(R2), -SR3, -OR3, Ar, or an alkyl group having 1-12 carbon atoms; Ar is an aromatic or heteroaromatic ring or fused ring having 3-10 carbon atoms within the ring structure, in which the heteroatom may be N, O, or S; R1 and R2 are independently selected from hydrogen, an alkyl group having 1-12 carbon atoms, or Ar as described above; R3 is an alkyl group having 1-12 carbon atoms, or is Ar as described above.

[0023] Examples of the inventive reworkable resin containing at least one aromatic urethane linkage and at least one reactive terminal group include:

[0024] The reworkable resin may also be formed by reacting one molar equivalent of a multifunctional isocyanate with the same number of molar equivalents of phenol or other alcohol compound containing acrylate, methacrylate, or styrenic functionality.

[0025] The reaction of an alcohol or phenol compound containing acrylate, methacrylate, or styrenic functionality with a multifunctional isocyanate proceeds according to the following reaction scheme:

[0026] The phenol or alcohol compound containing acrylate, methacrylate, or styrenic functionality will have the structure as shown in the above reaction scheme, in which A is selected from the group consisting of hydrogen, aliphatic, cycloaliphatic, and aromatic groups; Y is selected from the group consisting of aliphatic, cycloaliphatic, and aromatic groups with or without heteroatom.

[0027] The multifunctional isocyanate will have the structure as shown in the above reaction scheme, in which X is selected from the group consisting of aliphatic, cycloaliphatic, and aromatic groups with or without heteroatom; n is an integer within the range from 2 to 100.

[0028] At least one of the X or Y of the reactant must contain an aromatic group in the case where the urethane is an aromatic urethane.

[0029] The reaction of a phenol compound containing styrenic functionality with a multifunctional isocyanate proceeds according to the following reaction scheme:

in which A and B are independently selected from the group consisting of hydrogen, aliphatic, cycloaliphatic, and aromatic groups; G is selected from the group consisting of -N(R1)(R2), -SR3, -OR3, Ar, or an alkyl group having 1-12 carbon atoms (Ar is an aromatic or heteroaromatic ring or fused ring having 3-10 carbon atoms within the ring structure, in which the heteroatom may be N, O, or S; R1 and R2 are independently selected from hydrogen, an alkyl group having 1-12 carbon atoms, or Ar as described above; R3 is an alkyl group having 1-12 carbon atoms, or is Ar as described above);

[0030] X is selected from the group consisting of aliphatic, cycloaliphatic, and aromatic groups with or without heteroatom; n is an integer within the range from 2 to 100.

[0031] The reaction of a phenol or alcohol containing vinyl ether functionality with a multifunctional isocyanate proceeds according to the following reaction scheme:

in which A and B are independently selected from the group consisting of hydrogen, aliphatic, cycloaliphatic, and aromatic groups; X and Y are selected from the group consisting of aliphatic, cycloaliphatic, and aromatic groups with or without heteroatom, but at least one of X or Y contain an aromatic group; n is an integer within the range from 2 to 100.

[0032] The reaction of a phenol or other alcohol containing epoxy functionalities with a multifunctional isocyanate proceeds according to the following reaction scheme:

Y-OH +

in which A is selected from the group consisting of hydrogen, aliphatic, cycloaliphatic, and aromatic groups; X and Y are selected from the group consisting of aliphatic, cycloaliphatic, and aromatic groups with or without heteroatom, and at least one of X or Y contain an aromatic group; n is an integer within the range from 2 to 100.

[0033] The reaction of a phenol or other alcohol containing vinyl ether functionality with a multifunctional isocyanate proceeds according to the following reaction scheme:

n

in which X and Y are selected from the group consisting of aliphatic, cycloaliphatic, and aromatic groups with or without heteroatom, and at least one of X or Y contain an aromatic group; n is an integer within the range from 2 to100.

[0034] Examples of the inventive reworkable resin containing at least one aromatic urethane linkage and at least one reactive terminal group include:

in which n ranges from 2-100

[0035] The reworkable resin may also be formed by reacting a 1:1 equivalent ratio of a phenol containing styrenic functionality with an isocyantate compound containing acrylate or methacrylate functionality.

[0036] The reaction of a phenol containing styrenic functionality with an isocyantate compound containing acrylate or methacrylate functionality proceeds according to the following reaction scheme:

[0037] The phenol containing styrenic functionality will have the structure as shown in the above reaction scheme, in which in which A and B and independently selected from the group consisting of hydrogen, aliphatic, cycloaliphatic and aromatic groups with or without heteroatom; G is selected from the group consisting of -N(R1)(R2), -SR3, -OR3, Ar, or an alkyl group having 1-12 carbon atoms (Ar is an aromatic or heteroaromatic ring or fused ring having 3-10 carbon atoms within the ring structure, in which the heteroatom may be N₁ O₁ or S; R1 and R2 are independently selected from hydrogen, an alkyl group having 1-12 carbon atoms, or Ar as described above; R3 is an alkyl group having 1-12 carbon atoms, or is Ar as described above).

[0038] The isocyanate compound containing acrylate or methacrylate functionality will have the structure as shown in the above reaction scheme, in which E is selected from the group consisting of hydrogen, aliphatic, cycloaliphatic and aromatic groups with or without heteroatom; Y is selected from the group consisting of aliphatic, cycloaliphatic, and aromatic groups with or without heteroatom.

[0039] Further examples of the inventive reworkable resin containing at least one aromatic urethane linkage and at least one reactive terminal group include:

[0040] Generic structures for reworkable aliphatic urethane resins include the following structures:

and

wherein SG₁ and SG₂ are spacer groups selected from the group consisting of a direct bond, and an aliphatic, cycloaliphatic or aromatic structure, with or without heteroatom; and RTG₁ and RTG₂ are reactive terminal groups selected from the group consisting of methacrylate, acrylate, styrenic, vinyl ether, and epoxy functionalities.

[0041] Specific compounds can be prepared according to the methods in Examples 13 to 15, that is, based on the conditions similar to TMXDI-Glycidol adduct and IPDI-Glycidol adduct using either ethylene glycol monovinyl ether or 2-hydroxylethyl (meth)acrylate. The resulting compounds are shown here:

and

[0042] (In the above structures and in the claims, the notationCH₃ (H) indicates alternatively a methylene group (CH₃) or a hydrogen atom (H), so that the molecule will have a methacrylate functionality when only CH₃ is present, and an acrylate functionality when only H is present.)

[0043] In another embodiment the inventive resin is a hybrid resin that can be prepared from a di- isocyanate in which the isocyanate groups have a different degree of reactivity. For example, a secondary urethane mono-adduct can be prepared according to the following reaction

[0044] The mono-adduct can then be reacted with glycidol to make a hybrid resin, that is one containing more than one reactive functionality, for example, epoxy and acrylate functionalities as shown.

[0045] The curing agent may be any conventional or latent curing agent for reworkable resin. Examples of curing agents include peroxides, superacids, imidazoles, imidazole derivatives, imidazole- anhydride adducts, dicyandiamide, tertiary amines, amine salts, organic metal salts, and, inorganic metal salts, phenols and mixtures thereof. Preferred curing agents are peroxides, a super acids, imidazoles, imidazole derivatives and imidazole-anhydride adducts. The curing agent will be present in about 0.1 to about 30 parts based on reactive resin.

[0046] The reworkable composition may optionally comprise a crosslinker, such as primary amine, secondary amine or tertiary amine. The crosslinker is free of aromatic urethane linkages.

[0047] Reactive diluents may also be included in the reworkable composition. The reactive diluents contain reactive functionality, for example, selected from the group consisting of maleimide, acrylate, methacrylate, vinyl ether, styrenic, cinnamyl, epoxy, cycloaliphatic epoxy, and a combination of those.

[0048] The reworkable composition optionally comprises additives such as fillers, defoamers, and adhesion promoters. Preferred fillers include silica, clay, talc, alumina, boron nitride, aluminum nitride and calcium carbonate. Exemplary defoamers include foam destroying polysiloxanes, polyacrylates and polyether modified methylalkyl polysiloxane copolymers. Exemplary adhesion promoters are silanes and polyvinyl butyrol. The optional additives may be added up to about 80 weight percent based on the total composition. One skilled in the art may adjust the amount of the optional components to the composition, without undue experimentation.

[0049] Upon curing, a reaction product of a crosslinked network of methacrylate, styrenic, vinyl ether, and/or epoxy functionalities are formed from the reworkable resin having a urethane linkage and the curing agent.

[0050] The reaction product is capable of softening under exposure to rework temperatures. The urethane linkage of the cured composition is sufficiently inert before the decomposition temperature, or rework temperature. The urethane linkage of the cured composition decomposes quickly at the decomposition temperature and allows for reworkabilty. The rework or decomposition temperature generally ranges from about 180° to about 25O⁰C.

[0051] The following examples are for purpose of illustration and are not intended to limit the scope of the invention in any manner.

EXAMPLES EXAMPLE 1 : PREPARATION OF ISOCYANATOETHYL METHACRYLATE/ BIS-PHENOL A ADDUCT

[0052] To a three-neck round bottom flask was added 2-isocyanatoethyl methacrylate (11.3 mL, 80.0 mmol), bisphenol A (9.13g, 80.0 mmol), and toluene (100 mL). The mixture was stirred and heated to 80⁰C. After homogeneous solution was obtained, 10 drops of NEt3 (triethyl amine) was added into the reaction solution. The reaction was followed by monitoring the signal of -NCO peak in IR spectra. After three hours, small peak of -NCO was observed by IR. Additional 10 drops of triethyl amine was added. After stirring for another two hours, no -NCO peak was observed and the solvent was removed in vacuum to give 100% yield of product with mp. ~80 ⁰C. The structure was confirmed by IR and NMR (Figure I).

EXAMPLE 2: PREPARATION OF POLYPROPYLENE GLYCOL)TOLUENE DIISOCYANATE/ GLYCIDOL ADDUCT

[0053] To a three-neck round bottom flask was added polypropylene glycol)toluene diisocyanate (23.9g, 20.0mmol -NCO), glycidol (1.48g, 20.0mmol), and toluene (50 mL). The mixture was stirred and heated to 60⁰C. After homogeneous solution was obtained, dibutyltin dilaurate (~3mg) was added into the reaction solution. The reaction was followed by monitoring the signal of -NCO peak in IR spectra. After three hours, no -NCO was observed by IR. After the reaction was cooled to room temperature, the solvent was removed in vacuum to give 100% yield of product. The structure was confirmed by IR, MALDI, and NMR (Figure II).

EXAMPLE 3: PREPARATION OF ISEUGENOL/ ISOCYANATOETHYL METHACRYLATE ADDUCT

[0054] To a three-neck round bottom flask was added isoeugenol (10.0 g, 60.9 mmol) and isocyanatoethyl methacrylate (9.45g, 60.9 mmol). The mixture was stirred and heated to 50 ⁰C. The reaction was followed by monitoring the signal of -NCO peak in IR spectra. After 3.5 hours, no -NCO was observed by IR and the reaction became very viscous. After the reaction was cooled to room temperature, the reaction product was solidified. NMR suggested there is remaining of the starting material, isoeugenol, in the product mixture. The product mixture was then dissolved in toluene and washed with 10% NaOH solution. After drying and removing the drying reagent, the solvent was removed in vacuum to give 15.8 g (80%) product. The structure was confirmed by IR and NMR (Figure III).

EXAMPLE 4: PREPARATION OF POLYMDI (METHYLENE DIPHENYL DIISOCYANATE)/ GLYCIDOL ADDUCT

[0055] To a three-neck round bottom flask was added a mixture of 55% polyMDI and 45% difunctional isomers of MDI (30.Og, 238mmol -NCO) and glycidol (17.6g, 238mmol), and toluene (50 mL). The mixture was stirred and heated to 60 ⁰C. The reaction was followed by monitoring the signal of -NCO peak in IR spectra. After three hours, no -NCO was observed by IR. After the reaction was cooled to room temperature, the solvent was removed in vacuum to give 100% yield of product. The structure was confirmed by IR and NMR (Figure IV).

EXAMPLE 5: PREPARATION OF METHYLENE DIPHENYL DIISOCYANATE/ GLYCIDOL ADDUCT

^\^_ι dibutyltin dilaurate

OCN' ^^ ^^ "NCO °

[0056] To a three-neck round bottom flask was added MDI (20.Og, 80.0mmol) and glycidol (11.9g, 160mmol), and dry acetone (50 mL). The mixture was stirred and heated to 70 °C. The reaction was followed by monitoring the signal of -NCO peak in IR spectra. After three hours, no -NCO was observed by IR. The reaction was cooled to room temperature and the solvent was removed in vacuum to give 100% yield of product. The structure was confirmed by IR and NMR (Figure Vl).

EXAMPLE 6: DEGRADATION OF ISOCYANATOETHYL METHACRYLATE/ BIS-PHENOL A ADDUCT (FROM EXAMPLE 1 )

[0057] Hot-stage IR analysis was performed on the isocyanatoethyl methacrylate/ bis-phenol A adduct from Example 1, at temperatures from 25° to 325°C with monitoring the formation of the NCO peak. As shown in Figure Vl, the isocyanatoethyl methacrylate/ bis-phenol A adduct started to degrade at 180⁰C.

[0058] The hot-stage IR was also conducted at 250 ⁰C (isotherm). As shown in Figure VII, the aromatic urethane degraded within 2 minutes at 250 ⁰C. [0059] Thermal gravimetric analysis (TGA) of the isocyanatoethyl methacrylate/ bis-phenol A adduct was performed at a heating rate of 10°C/minute. As shown in Figure VIII₁ the isocyanatoethyl methacrylate/ bis-phenol A adduct resulted in 10% weight loss at 260⁰C.

EXAMPLE 7: DEGRADATION OF POLYPROPYLENE GLYCOL)TOLUENE DIISOCYANATE/ GLYCIDOL ADDUCT (FROM EXAMPLE 2)

[0060] TGA of the poly(propylene glycol)toluene diisocyanate/ glycidol adduct was performed at a heating rate of 10°C/minute. The adduct resulted 10% weight loss at 252°C.

EXAMPLE 8: DEGRADATION OF ISEUGENOL/ ISOCYANATOETHYL METHACRYLATE ADDUCT (FROM EXAMPLE 3)

[0061] TGA of the iseugenol/ isocyanatoethyl methacrylate adduct was performed at a heating rate of 10°C/minute. The adduct resulted10% weight loss at 199⁰C.

EXAMPLE 9: DEGRADATION OF POLYMDI (METHYLENE DIPHENYL DIISOCYANATE)/ GLYCIDOL ADDUCT (FROM EXAMPLE 4)

[0062] TGA of the poly M Dl (Methylene diphenyl diisocyanate)/ glycidol adduct was performed at a heating rate of 10°C/minute. The degradation of the adduct initiated from about 200 ⁰C.

EXAMPLE 10: DEGRADATION OF METHYLENE DIPHENYL DIISOCYANATE/ GLYCIDOL ADDUCT (FROM EXAMPLE 5)

[0063] TGA of the MDI (Methylene diphenyl diisocyanate)/ glycidol adduct was performed at a heating rate of 10°C/minute. The degradation of the adduct initiated from about 150⁰C.

EXAMPLE 11. PHYSICAL PROPERTIES OF REWORKABLE UNDERFILL

[0064] A sample of an underfill (Sample 1) was prepared with (poly M Dl (Methylene diphenyl diisocyanate)/ glycidol adduct (from Example 4) with 6% 2MZ Azine (Air Products, PA) curing agent. The mixture was cured at 120⁰C for 30 minutes. Comparative underfill samples were prepared in the same manner. Comparative A is an analogous formulation to Sample 1 , but without the urethane segment of Example 4. Comparative B and C samples are commercially available reworkable underfills. The Tg and CTE values are reported in Table 1.

Example 4

¹ TMA method

² for temperature range of -40⁰C to -2O⁰C

³ for temperature range of 65⁰C to 85⁰C

⁴ XE 1218, cycloaliphatic epoxy with polyester diol based underfill; Emerson & Cuming, Billerica, MA

⁵ E1220M2, cycloaliphatic epoxy, polyester diol, divinyl ether based underfill; Emerson & Cuming, Billerica, MA

[0065] Sample 1 has a much higher Tg, and a significantly lower CTE (alphal) than the commercially available reworkable underfills. Higher Tg values have been shown to significantly increase the thermal cycle resistance of underfilled CSP, BGA₁ and PoP devices. In a thermal cycle test of 14mm x 14 mm PoP devices underfilled with sample 1 and comparative examples, sample 1 was shown to provide superior performance.

¹Thermal cycle range was -40⁰C to 85°C 2Thermal cycle range was -40⁰C to 115⁰C EXAMPLE 12. REWORKABILITY

[0066] The reworkable underfills of Example 11 were dispensed onto at least three chip scale packages (CSPs) and then connected and cured to a printed circuit board (PCB) to form electronic devices. To rework, the devices were heated to 250⁰C for one minute and then the CSPs were removed from the PCB. The following factors were tested and recorded in Table 3 to determine reworkablilty: (a) force required to remove the CSP from the PCB with a metal bar (v low; low; med; med high; high; not removable)

(b) amount of underfill residue remaining on the board after removal (area %)

(c) amount of damage to the copper pads on the board (points of electrical connection)

(d) amount of damage to the electrical traces on the board (%)

(e) amount of damage to the solder mask coating on the board (area %)

(f) amount of time required to clean the board of the residual underfill (minutes).

[0067] Table 3 indicates that Sample 1 was easier to remove, left less residual underfill on the board, caused less damage to the solder mask and allowed faster removal of the underfill than the non- reworkable analog (Comparative C), and was comparable to commercial reworkable underfills, comparative A and B.

EXAMPLE 13: PREPARATION OF TMXDI-GLYCIDOL ADDUCT IN THF

DBTDL

[0068] Into a 1 L four neck round bottom flask was added 120.1 g of m-tetramethyl diisocyanate (m- TMXDI) (Aldrich, 98.6% purity) and 121 g of tetrahydrofuran (THF). The flask was equipped with an overhead stirrer, and nitrogen tube. The solution was warmed to an internal temperature of 45⁰C and 10 ppm of dibutyl tin dilaureate (based on adduct) was added to the isocyanate solution. A total of 76.9 g of glycidol (Aldrich, 99.6%) was added to the reaction vessel via a slow addition funnel over a period of one hour. The reaction continued for another six hours. The reaction was cooled to room temperature and held overnight without stirring. The following day reaction contained a small amount of un-reacted NCO as determined by FT-IR. The reaction was re-heated to 55⁰C and 0.5 g of glycidol was added. Reaction was complete after one hour at 55⁰C giving a clear semisolid.

EXAMPLE 14: PREPARATION OF TMXDI-GLYCIDOL ADDUCT IN EPOXIES

[0069] Into a 250 mL three neck round bottom flask was added 39.1O g of 50/50 bisphenol-A diglycidyl ether/bisphenol-F diglycidyl ether, 19.55 g of butanediol diglycidyl ether, and 19.1Og of glycidol. The flask was equipped with an overhead stirrer, and nitrogen tube. The solution was warmed to an internal temperature of 55 ⁰C and 10 ppm of dibutyl tin dilaureate (based on adduct) was added to the epoxy solution. A total of 30.00 g of m-tetramethyl diisocyanate (m-TMXDI) (Aldrich, 98.6% purity) was added to the reaction vessel via a slow addition funnel over a period of 1 hour. The reaction continued for another 4 hours. The reaction was cooled to room temperature and held overnight without stirring. The following day reaction contained un-reacted NCO as determined by FT-IR. The reaction was re-heated to 65 ⁰C and held for an additional 4 hours at 65 ⁰C. The product is a clear liquid with a viscosity of 2,211 cP (25 ⁰C, Brookfield DVII, spindle #51 , 10rpm).

EXAMPLE 15: PREPARATION OF IPDI-GLYCIDOL ADDUCT IN THF

DBTDL

[0070] Into a 100 mL three neck round bottom flask was added 10.01 g of isophorone diisocyanate (IPDI) (Aldrich, 98% purity) and 50 g of tetrahydrofuran (THF). The flask was equipped with an overhead stirrer, and nitrogen tube. The solution was warmed to an internal temperature of 45⁰C and 0.075 weight % of dibutyi tin dilaureate (based on adduct) was added to the isocyanate solution. A total of 6.86 g of glycidol (99.6%) was added to the reaction vessel via a slow addition funnel over a period of 30 minutes. The reaction temperature was increased to 65 ⁰C and stirred for 6 hours at which point the reaction was judge complete by the absents of NCO by FT-IR. The product is a clear, semisolid.

EXAMPLE 16: PREPARATION OF SECONDARY URETHANE MONO-ADDUCT FOR A HYBRID RESIN

[0071] Into a small plastic jar were mixed 11.1g IPDI, 10.7g 3-(acryloyloxy)-2-hydroxypropyl methacrylate (Aldrich), and 0.002Og dibutyltin dilaureate. The sample was allowed to react at room temperature for 48h. ¹HNMR revealed that 68.3% of IPDI were converted to the secondary urethane mono-adduct.

EXAMPLE 17

[0072] A comparison of four formulations with respect to their thermal reworkability was conducted. The reworkability score was calculated using an in-house formula based on the criteria listed in Table 3, Example 12. All urethane epoxy based formulations showed significantly better rework performance.

[0073] Many modifications and variations of this invention can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments described herein are offered by way of example only, and the invention is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. A reworkable resin comprising at least one aromatic urethane group, wherein an aromatic group is directly connect to the N atom, O atom or both the N and the O atoms of a urethane and at least one reactive terminal group, wherein the reactive terminal group is selected from the group consisting of methacrylate, acrylate, styrenic, vinyl ether and epoxy functionalities.

2. The compound according to claim 1 having a structure selected from the group consisting of:

and

in which

A and B are independently selected from the group consisting of hydrogen, aliphatic, cycloaliphatic and aromatic groups with or without heteroatom;

X and Y are independently selected from the group consisting of aliphatic, cycloaliphatic, and aromatic groups, with or without heteroatom;

G, Q, and J are independently selected from the group consisting of -N(R1)(R2), -SR3, -0R3, Ar, or an alkyl group having 1-12 carbon atoms;

Ar is an aromatic or heteroaromatic ring or fused ring having 3-10 carbon atoms within the ring structure, in which the heteroatom may be N, O, or S;

R1 and R2 are independently selected from hydrogen, an alkyl group having 1-12 carbon atoms, or Ar; R3 is an alkyl group having 1-12 carbon atoms, or is Ar; n is an integer within the range from 2-100.

3. The compound according to claim 1 or 2 having a structure selected from the group consisting of:

in which n is an integer within the range from 2 to 100.

4. A reworkable aliphatic urethane resin selected from the group consisting of

and

wherein SG₁ and SG₂ are selected from the group consisting of a direct bond, an aliphatic, a cycloaliphatic and an aromatic structure, with or without heteroatom; and RTG₁ and RTG₂ are reactive terminal groups selected from the group consisting of methacrylate, acrylate, styrenic, vinyl ether, and epoxy functionalities.

5. The compound according to claim 4 having a structure selected from the group consisting of:

and

6. A hybrid compound having a functionality selected from the group consisting of acrylate, methacrylate, styrenic, vinyl ether, epoxy, and combinations thereof, and a urethane linkage.

7. A thermally reworkable composition, said composition comprising the cured product of: a. a resin having (1) at least one urethane group, and (2) at least one reactive terminal group; and b. a curing agent; wherein said composition is substantially anhydride-free and thermally degrades from about 18O⁰C to about 275⁰C.

8. The thermally reworkable composition of claim 7, wherein the reactive terminal group is selected form the group consisting of acrylate, methacrylate, styrenic, vinyl ether and epoxy functionalities.

9. The thermally reworkable composition of claim 7, wherein the curing agent is selected from the group consisting of peroxides, a super acids, imidazoles, imidazole derivatives, imidazole-anhydride adducts and mixtures thereof.

10. A thermally reworkable composition comprising the cured product of: (a) a resin having (1) at least one urethane group, and (2) at least one reactive terminal group; and (b) a curing agent, in which the resin is a resin as claimed in claim 2 or claim 4.

11. A thermally reworkable composition comprising the cured product of: (a) a resin having (1 ) at least one urethane group, and (2) at least one reactive terminal group; and (b) a curing agent, in which the resin is a resin as claimed in claim 3 or claim 5.

12. An article comprising a first substrate bonded to at least a second substrate with a thermally reworkable composition of any one of claims 2 to 5, wherein at least one of the substrate is an electronic component and/or a semiconductor chip.

13. A solvent free process of making a urethane epoxy resin comprising

1. Premixing epoxy resins with glycidol having a purity above 99.5%

2. Adding to the above epoxy mixture, a catalyst suitable for hydroxyl-isocyanate addition

3. Slowly adding an isocyanate compound to the above mixture at a temperature ranging from 20 to 100 degree C, preferably between 40-60 degree C.